This invention relates to large vertical-shaft machines, and in particular it relates to the supplementary cooling of the thrust bearings used in such machines.
Thrust bearings for large vertical-shaft machines usually comprise a downwardly facing ring that is mounted to the rotating component of the machine and a plurality of shoes or bearing segments with upwardly directed bearing surfaces. The bearing segments support the rotating ring on an oil film which is usually provided by having the ring and the bearing segments submerged in an oil bath.
The shoes are mounted on a pivot, or by some other means that permits a limited pivotting action, so that the shoe segment is able to tilt down slightly at the leading edge to form the oil film into a slight wedge-shaped configuration. The tilting action also provides for alignment of the shoe surface with the surface of the rotating ring.
The bearing shoes may each be supported on a single pivot, or may be supported by a plurality of springs, or by distributed discs as described in U.S. Pat. No. 2,565,116--Baudry, issued Aug. 21, 1951, or by mechanical support elements having different mechanical characteristics to provide different, desired, compressive strains as described in Canadian Patent No. 1,116,671 --Starcevic, issued Jan. 19, 1982, or by a plurality of distributed hydraulic elements as described in copending Canadian application, Serial No. 490,652 --Bath, filed Sept. 13, 1985. All these are able to provide the required wedge-shaped oil film between the surface of the shoe and the surface of the rotating ring. There is movement or flow of this oil film which transfers some of the heat generated by the moving surfaces from those surfaces into the oil bath.
Depending on the load per unit area and other factors, the flow of oil across the bearing surfaces may not carry a sufficient quantity of heat from the surfaces. It may be necessary to provide for additional heat dissipation or removal. One way of providing for additional heat removal is by using forced circulation of a coolant through passages in the shoes. This, of course, requires an external pump and means to power the pump. This introduces further complexity.